1. Technical Field of the Invention
The present invention relates to a carrier conveying apparatus which is suitable for conveying carriers or the like in which, for example, substrates to be processed are accommodated and also relates to an elevating mechanism installed in the carrier conveying apparatus. In addition, the invention relates to a heat treatment installation.
2. Description of the Related Art
In general, a production process of semiconductor devices includes various steps of applying an oxidation process, diffusion process and CVD process etc. on semiconductor wafers as objects to be processed. Thus, in view of the improvement of throughput, cleanness and space-conserving etc. of these steps, a variety of processing apparatuses have been proposed [e.g. see Japanese Unexamined Patent Publication (Kokai) No. 4-133422].
For example, the processing apparatus disclosed in the above publication includes a vertical heat treatment furnace arranged on a rear and upper side inside a casing of the apparatus, for heat-treating a great number of wafers at a time, using a wafer boat as a carrier for objects to be processed. On the front side of the casing, a carrier input/output port (also called an I/O port) is provided for inputting and outputting a carrier as a container for accommodating a plurality of wafers therein.
Inside the above-mentioned casing, there are provided a carrier keeping section which is positioned on an upper side of the casing close to the carrier I/O port, for keeping a plurality of carriers; a carrier set-up section and a wafer boat set-up section both of which are arranged between the carrier I/O port and the heat treatment furnace, for delivering the wafers between the carrier and the wafer boat; and a wafer conveying mechanism for delivering the wafers between the carrier set-up section and the wafer boat set-up section. Further arranged in the casing is a carrier conveying apparatus with an elevating mechanism, which carries out the delivery of carriers between the carrier I/O port and the carrier keeping section, between the carrier keeping section and the carrier set-up section or between the carrier I/O port and the carrier set-up section.
Since it is necessary that, in the carrier conveying apparatus, the elevating mechanism has a relatively large stroke of e.g. 3 m to 5 m and the difficulty that the elevating mechanism employs a ball screw, a mechanism to elevate an elevating mechanism suspended by a wire or a timing belt as a suspension member is adopted as the elevating mechanism. Despite high strength in the suspension member, it is expected that if the suspension member is broken off, then utensils might be damaged because of the drop of such a heavy elevating mechanism weighing 70 to 80 kg, for example. Therefore, the above elevating mechanism is so constructed that, when a sensor detects the cutting of the suspension member, the elevating mechanism is stopped by a brake mechanism, thereby preventing the mechanism from falling.
In the above-mentioned elevating mechanism, however, it is necessary to provide a sensor for detecting the cutting of the suspension member and a control unit with electric circuits for controlling the brake mechanism by inputting a signal from the sensor etc. Therefore, with the increase in manufacturing cost and necessity of using electricity, there is a possibility that the elevating mechanism will have a faulty operation due to misidentification by the sensor.
Accordingly, it is therefore an object of the present invention to provide an elevating mechanism which is capable of mechanically stopping an elevating mechanism, not electrically, when the suspension member is broken off, whereby the elevating mechanism can be prevented from falling and to also provide a carrier conveying apparatus having the elevating mechanism.
According to the first feature of the invention, there is a provided an elevating mechanism comprising:
a guide member arranged along a vertical direction;
a fixed surface arranged in parallel with the guide member;
an elevating mechanism guided so as to rise and fall along the guide member;
a braking mechanism pivotally supported by the elevating mechanism in a vertical plane, the braking mechanism being in a position apart from the fixed surface under a normal condition of the braking mechanism and being rotated in a direction approaching the fixed surface from an underside of the elevating mechanism when the elevating mechanism falls, whereby the braking mechanism is engaged with the fixed surface to brake the elevating mechanism;
urging means for urging the braking mechanism to rotate in the direction approaching the fixed surface from the underside of the elevating mechanism;
a suspension member connected to the braking mechanism, for suspending the elevating mechanism through an intermediary of the braking mechanism, the suspension member, owing to its tensile strength to suspend the elevating mechanism, also rotationally urging the braking mechanism in a direction to separate the braking mechanism from the fixed surface in opposition to the rotating force due to the urging means; and
a stopper for stopping the rotation of the braking mechanism due to the tensile strength of the suspension member;
said stopper including:
a stopper member fixed to said braking mechanism, said stopper member having a stopper surface; and
an abutment member fixed to said elevating mechanism, said abutment member having an abutment surface;
whereby, said stopper stops the rotation of said braking mechanism due to the tensile strength of said suspension member by engaging said abutment surface with said stopper surface of said stopper member:
whereby, when the suspension member is cut off, the braking mechanism to which urging force due to the tensile strength of the suspension member is not applied any longer is rotated against the fixed surface by the urging means, so that the elevating mechanism can be braked.
According to this feature, when the suspension member is cut off, it is possible to stop the elevating mechanism mechanically, and not electrically, so that the elevating mechanism can be prevented from falling.
The second feature of the invention resides in a carrier conveying apparatus comprising:
a fixed frame arranged so as to extend in a vertical direction;
a supporting arm adapted so as to move in the vertical direction along the fixed frame, for conveying a carrier having an object to be processed accommodated therein; and
an elevating mechanism arranged between the fixed frame and the supporting arm, for moving the supporting arm to a predetermined position in the vertical direction and maintaining the supporting arm thereat so as not to fall down, the elevating mechanism including:
a guide member arranged on the fixed frame along a vertical direction;
a fixed surface arranged in parallel with the guide member;
an elevating mechanism guided so as to rise and fall along the guide member, for supporting the supporting arm;
a braking mechanism pivotally supported by the elevating mechanism in a vertical plane, the braking mechanism being in a position apart from the fixed surface under a normal condition of the braking mechanism and being rotated in a direction approaching the fixed surface from an underside of the elevating mechanism when the elevating mechanism falls, whereby the braking mechanism is engaged with the fixed surface to brake the elevating mechanism;
urging means for urging the braking mechanism so as to rotate in the direction approaching the fixed surface from the underside of the elevating mechanism;
a suspension member connected to the braking mechanism, for suspending the elevating mechanism through an intermediary of the braking mechanism, the suspension member, owing to its tensile strength to suspend the elevating mechanism, also rotationally urging the braking mechanism in a direction to separate the braking mechanism from the fixed surface in opposition to rotating force due to the urging means; and
a stopper for stopping the rotation of the braking mechanism due to the tensile strength of the suspension member;
said stopper including:
a stopper member fixed to said braking mechanism, said stopper member having a stopper surface; and
an abutment member fixed to said elevating mechanism, said abutment member having an abutment surface;
whereby, said stopper stops the rotation of said braking mechanism due to the tensile strength of said suspension member by engaging said abutment surface with said stopper surface of said stopper member;
whereby, when the suspension member is cut off, the braking mechanism to which urging force due to the tensile strength of the suspension member is not applied any longer is rotated against the fixed surface by the urging means, so that the elevating mechanism can be braked from falling.
According to this feature, when the suspension member is cut off, it is possible to stop the elevating mechanism without depending on an electrical method but a mechanical method instead certainly, thereby preventing the elevating mechanism from falling. Particularly, in conveying a carrier for an expensive and heavy semiconductor wafer, it is possible to prevent the wafer from being damaged by falling and prevent control instruments disposed under the supporting arm from being damaged.
The third feature of the invention resides in the carrier conveying apparatus wherein the braking mechanism includes:
a shaft for rotating the braking mechanism;
a braking member arranged so as to project from the shaft radially outward, the braking member, at a time of the elevating mechanism falling down, being rotationally forced between the shaft and the fixed surface thereby to press the fixed surface; and
a suspension member connecting part arranged across the shaft from the fixed surface, the suspension member connecting part having the suspension member connected thereto.
According to this feature, since the suspension member is connected to the suspension member connecting part disposed across the shaft from the fixed surface, it is possible to avoid the braking member rotating toward the fixed surface due to the suspension member vibrations or the like, thereby preventing the wrong operation of the braking member. Further, since the carrier conveying apparatus is adapted so as to force the braking member between the shaft and the fixed surface from the underside at the time of the elevating mechanism falls down, it is possible to lock the braking member on the fixed surface securely, so that the elevating mechanism can be stopped.
The fourth feature of the invention resides in the carrier conveying apparatus wherein the braking member has a press surface formed on a leading end thereof to be pressed on the fixed surface, the press surface being formed in a manner that a distance between the press surface and the shaft increases in the opposite direction to the rotating direction of the braking member.
The fifth feature of the invention resides in the carrier conveying apparatus wherein the braking member is provided, on the press surface, with a tooth part which encroaches on the fixed surface when the braking member is pressed against the fixed surface.
The sixth feature of the invention resides in the carrier conveying apparatus wherein the braking member is shaped in the form of a lever.
The seventh feature of the invention resides in the carrier conveying apparatus wherein the urging means comprises a tensile spring.
The eighth feature of the invention resides in the carrier conveying apparatus wherein the urging means comprises a weight.
The ninth feature of the invention resides in the carrier conveying apparatus wherein the suspension member is a toothed belt.
The tenth feature of the invention resides in the carrier conveying apparatus wherein the suspension member is a wire.
The eleventh feature of the invention resides in the carrier conveying apparatus wherein the fixed surface is made of aluminum.
The twelfth feature of the invention resides in the carrier conveying apparatus wherein the fixed surface is provided, thereon, with an engagement projection and wherein the braking mechanism comprises:
a shaft for allowing the braking mechanism to be rotated;
an engagement member arranged so as to project from the shaft radially outward, the engagement member having a leading end thereof formed for engagement with the engagement projection on the fixed surface; and
a suspension member winding part about which the suspension member is wound, the suspension member winding part being rotatable about the shaft.
According to this feature, since the engagement projection is adapted so as to engage with the engagement member, it is possible to carry out braking and stopping for the elevating mechanism.
The thirteenth feature of the invention resides in the carrier conveying apparatus wherein the engagement member is provided, at a tip thereof, with a claw part for engagement with the engagement projection on the fixed surface.
The fourteenth feature of the invention resides in the carrier conveying apparatus wherein the suspension member is a toothed belt.
The fifteenth feature of the invention resides in the carrier conveying apparatus wherein the urging means comprises a tensile spring.
The sixteenth feature of the invention resides in the carrier conveying apparatus wherein the urging means comprises a torsion spring which is wound about the shaft.
According to a still further feature, the present invention also relates to a heat treatment installation including a carrier I/O port for receiving and taking out a carrier which accommodates a substrate;
a carrier keeping section for keeping the carrier;
a carrier set-up section where the carrier is set-up for receiving and taking out the substrate;
a heat treatment apparatus for heat-treatment of the substrate;
a substrate conveyer mechanism for conveying the substrate between the carrier set-up section and the heat treatment apparatus;
a carrier conveying apparatus for conveying the carrier between the I/O port, the carrier keeping section and the carrier set-up section, the carrier conveying apparatus including:
a fixed frame arranged so as to extend in a vertical direction;
a supporting arm adapted so as to move in the vertical direction along said fixed frame, for conveying a carrier having an object to be processed accommodated therein; and
an elevating mechanism arranged between said fixed frame and said supporting arm, for moving said supporting arm to a predetermined position in the vertical direction and maintaining said supporting arm thereat so as not to fall down, said elevating mechanism including:
a guide member arranged on said fixed frame along a vertical direction;
a fixed surface arranged in parallel with said guide member;
an elevating mechanism guided so as to rise and fall along said guide member, for supporting said supporting arm;
a braking mechanism pivotally supported by said elevating mechanism in a vertical plane, said braking mechanism being in a position apart from said fixed surface under a normal condition of said braking mechanism and being rotated in a direction approaching said fixed surface from an underside of said elevating mechanism when said elevating mechanism falls, whereby said braking mechanism is engaged with said fixed surface to brake said elevating mechanism;
urging unit for urging said braking mechanism to rotate in the direction approaching said fixed surface from the underside of said elevating mechanism;
a suspension member connected to said braking mechanism, for suspending said elevating mechanism through an intermediary of said braking mechanism, said suspension member, owing to its tensile strength to suspend said elevating mechanism, also rotationally urging said braking mechanism in a direction to separate said braking mechanism from said fixed surface in opposition to the rotating force due; and
a stopper including:
a stopper member fixed to said braking mechanism, said stopper member having a stopper surface; and
an abutment member fixed to said elevating mechanism, said abutment member having an abutment surface;
whereby, said stopper stops the rotation of said braking mechanism due to the tensile strength of said suspension member by engaging said abutment surface with said stopper surface of said stopper member;
whereby, when said suspension member is cut off, said braking mechanism to which urging force due to the tensile strength of said suspension member is not applied any longer is rotated against said fixed surface by said urging unit, so that said elevating mechanism can be braked.